Fabrication and Characterization of Natural Fiber Reinforced Cowpea Resin-based Green Composites: an Approach Towards Agro-waste Valorization

A paradigm shift towards using bio-resins or bio-derived resins among materials scientists has led to wide exploration of the sector. Polymers such as soy protein isolate, poly(hydroxy alkanoate), poly(lactic acid), and thermoplastic starch are all synthetically modified bio-based resins and are costly. The cowpea-derived resin with the least chemical modification was used in this study as a matrix for the formation of composites with natural fibers at a lesser cost. Fabrication of composites of vetiver and jute with varying weight percentages of fiber (50, 60, and 70%) in the innovative cowpea resin resulted in favorable mechanical properties and degradability. The tensile strength was the highest for the jute-cowpea composite (JCP2) at around 37.49 MPa, which also has a flexural strength of 40.3 MPa. Dynamic mechanical analysis of composites reflects the moderate storage moduli of 1802 MPa for JCP2 and 1351 MPa for vetiver-cowpea (VRCP2) composites. Impact strength studies and thermal stability also show optimistic results. The contact angle, water absorption behavior, and swelling in thickness show the moderate hydrophobicity of the composites. This is also a reason for the improved degradability of the composites in soil-burial and microbial environments. Characterizations such as FE-SEM and FTIR spectroscopy, conducted after the degradation of the samples, showcased the level of deterioration. All these results suggest using the innovative cowpea resin as a good alternative to various other synthetic thermoplastic resins used in the fiber reinforced composite manufacturing field.